Configuring your Application

Configuration is performed within the src/config.rs file, which defines a configuration factory function that returns a JSON object.

To customize your application build, use the env! and option_env! Rust macros to read environment variables at build time. This will hard-code their final values into your sealed wasm bundle, ensuring scrict release versioning and optimal security.

Configuring your Adapter

One common use case is the need to configure your application's adapters with the URL of your back-end API service. To achieve that, your configuration might look like this:

// src/config.rs
pub fn new() -> serde_json::Value {
    serde_json::json!({
        "api_url": option_env!("API_URL").unwrap_or("http://localhost:3000"),
    })
}

or

// src/config.rs
pub fn new() -> serde_json::Value {
    serde_json::json!({
        "api_url": env!("API_URL").expect("an API_URL is required to build"),
    })
}

At build time, you would provide the API URL during calls to make as follows for a test environment:

$ API_URL=https://api.test.yourapp.yourdomain make

or for a production environment:

$ API_URL=https://api.yourapp.yourdomain make

On application startup, adapters have their init() function invoked, which is where the config is passed in as a parameter.